ReadyBoost ready, but doesn't boost

Vista's ReadyBoost feature, which theoretically improves performance by placing part of Vista's memory swapfile onto a highspeed flash drive, is one of the slickest OS tricks we've heard about in a long time. Unfortunately, it isn't as sweet in practice, according to PC World. They tested three USB flash drives by Kingston, Lexar, and Ridata that claim to be ReadyBoost, uh, ready, and found that while they were able to measure a slight speedup in certain activities (like opening frequently-used applications) overall the effect was unnoticeable